Noise and spectral stability of deep-UV gas-filled fiber-based supercontinuum sources driven by ultrafast mid-IR pulses

TL;DR

This study investigates the noise and spectral stability of deep-UV supercontinuum sources generated in gas-filled hollow-core fibers, highlighting the importance of pump laser stabilization for improving noise performance.

Contribution

It provides experimental and numerical analysis of noise characteristics in gas-filled fiber supercontinuum sources, emphasizing the role of pump laser RIN in spectral stability.

Findings

Spectral stability over 110 hours without degradation.

RIN of 33.3% observed at 275 nm DW.

Pump laser RIN significantly affects noise performance.

Abstract

Deep-UV (DUV) supercontinuum (SC) sources based on gas-filled hollow-core fibers constitute perhaps the most viable solution towards ultrafast, compact, and tunable lasers in the UV spectral region. Noise and spectral stability of such broadband sources are key parameters that define their true potential and suitability towards real-world applications. In order to investigate the spectral stability and noise levels in these fiber-based DUV sources, we generate an SC spectrum that extends from 180 nm (through phase-matched dispersive waves - DWs) to 4 {\mu}m by pumping an argon-filled hollow-core anti-resonant fiber at a wavelength of 2.45 {\mu}m. We characterize the long-term stability of the source over several days and the pulse-to-pulse relative intensity (RIN) noise of the strongest DW at 275 nm. The results indicate no sign of spectral degradation over 110 hours, but the RIN of the DW pulses at 275 nm is found to be as high as 33.3%. Numerical simulations were carried out to investigate the spectral distribution of the RIN and the results confirm the experimental measurements and that the poor noise performance is due to the RIN of the pump laser, which was hitherto not considered in numerical modelling of these sources. The results presented herein provide an important step towards an understanding of the noise mechanism underlying such complex light-gas nonlinear interactions and demonstrate the need for pump laser stabilization.